1. Field of the Invention
The present invention is directed to a safety system for transfer of pressurized fluids. In particular, the present invention is directed to an automatic shutoff system for transfer of pressurized fluids from a cargo tank vehicle to a storage container through a delivery hose.
2. Prior Art
Pressurized fluids, such as compressed liquid gases, are utilized in a variety of applications. Liquified compressed gases include carbon dioxide (CO.sub.2), butane (C.sub.4 H.sub.10), anhydrous ammonia (NH.sub.3), and propane(C.sub.3 H.sub.8). Propane and butane (known commercially as LP gas or LPG) have an extremely wide range of domestic, industrial, and agricultural uses. Among the uses are appliance fuel, industrial and utility furnaces, industrial heating processes such as heat treating and metal cutting, and vehicle fuel. Liquified compressed gases generally are those which become liquids in containers at ordinary temperatures at pressures from 25 to 2500 psig. As an example, the pressure of liquid propane at 70.degree. F. (21.1.degree. C.) is approximately 110-125 psig (756.4 KiloPascal KPa).
Liquified compressed gases are categorized as hazardous materials. Those who transport compressed gases must comply with a variety of government safety regulations in the United States, Canada and other countries throughout the world. Liquified compressed gases are shipped under rules that limit the maximum amount that can be put into a container to allow space for liquid expansion. For example, in the United States, a cargo tank (defined as a tank permanently attached to or forming a part of a motor vehicle) selected for transporting a specific compressed gas must be a container authorized for that product and the container must be qualified with Department of Transportation (DOT) regulations. These regulations are contained in Title 49 of the Code of Federal Regulations, Parts 100 to 199.
Additionally, with flammable gases, it is necessary to guard against the possibility of fire or explosion. For example, when liquid propane is released into the atmosphere, it quickly vaporizes into its normal non-pressurized gaseous form. The propane combines rapidly with air to form fuel-air mixtures which are ignitable over a range of 2.2 to 9.5% by volume.
In the liquified compressed gas industry, transportation between the producer and the consumer is important. In many instances, the producer and consumer are separated by considerable distances. Large quantities of compressed gas must be transported over long distances by safe and economical methods. Liquified compressed gases are often transported in special tank cars, motor trucks, boat and train facilities.
For example, the propane industry in the U.S. transports between 7 and 10 billion gallons annually in highway transport vehicles to storage sites. The same volume is transported again from storage sites in local delivery bobtail trucks to storage containers.
Cargo tank motor vehicles have been developed to transfer liquified compressed gases. Two basic types are well known. Cargo tank motor vehicles known as "highway transports" are large cargo tanks mounted on semi trailers pulled by a highway truck tractor. A typical transport may carry 9000-16000 gallons of liquid. Cargo tanks must comply with DOT Specification MC-330 or MC-331. Smaller cargo tank motor vehicles, known as "bobtails", are cargo tanks mounted directly on a vehicle chassis. A bobtail may carry up to 5000 gallons of liquid.
In each type, a pump on the vehicle is powered by the vehicle engine, meaning that the engine must remain on during unloading.
In the case of highway transports, liquified compressed gas is transferred from the highway transport to a storage container by means of a hose. A pump is mounted on the highway transport to move the liquified gas from the cargo tank, through the hose and into the storage container. A pump valve is located on the highway transport between the cargo tank and the pump. The pump valve may be operated manually by the operator or may have an automatic feature that will close the valve in the event of a drop in the pressure.
In the case of bobtails, liquified compressed gas is transferred from the bobtail storage tank to a storage container by means of a hose.
Notwithstanding the foregoing, the existing vehicle belly valve may not be automatically activated in the event of a rupture, a severing or uncoupling of the hose. Most recently, the U.S. Department of Transportation has announced proposed rules and interim rules relating to emergency discharge control systems on cargo tanks (see, for example, 49 CFR .sctn.178).
For these reasons, there still remains a need for an automatic safety shutoff system in the event of a rupture, severing or uncoupling of a delivery hose between a cargo tank vehicle and a storage container.
It is, therefore, a principal object and purpose of the present invention to provide an automatic safety shut off system in the event of a rupture, severing, or uncoupling of a delivery hose between a cargo tank vehicle and a storage container.